A federal judge on Monday let stand a 2018 lawsuit that charges 3M and other companies with causing potentially toxic PFAS chemicals to collect in human bodies.

The lead plaintiff in the Ohio case that Judge Edmund Sargus Jr. refused to dismiss is Kevin Hardwick. He is a former Ohio firefighter who said he has per- and polyfluoroalky substances (PFAS) in his blood because he was exposed to the chemicals for 40 years in his job.

The lawsuit's named defendants include Maplewood-based 3M, DuPont and Chemours.

"While we are disappointed with the decision, this case is in its earliest stages," 3M said in a statement. "3M acted responsibly in connection with products containing PFAS and we will continue to vigorously defend our record of environmental stewardship."

The company has steadfastly maintained — most recently during a congressional hearing — that PFAS have not caused any human health injuries at the levels at which they are present in the environment.

PFAS are used for many uses including waterproofing, stain and heat resistance, and firefighting foam. They have been found in drinking water of millions of Americans, as well as in groundwater, soil, firefighting foam, animals and food packaging, as well as humans.

The EPA has warned about PFAS' potential links to cancer, immune issues and reproductive problems, among other conditions. Their spread to hundreds of sites across the country spawned dozens of bills in the current session of the U.S. Senate and House, as well as legislation and regulation in some states.

Critics of the chemicals said Hardwick's case, if successful, could eventually draw in tens of millions of people in the country with detectable levels of PFAS in their blood.

3M and other defendants asked Sargus to dismiss the Hardwick case because it failed to state a specific claim and because there were jurisdictional issues.

Sargus said Hardwick sufficiently argued that 3M and other defendants had used or distributed PFAS in Ohio in such a way that Hardwick's blood and body became contaminated with PFAS while in the state.

The judge called his action a "threshold determination" and warned that Hardwick would still have to prove the facts upon which he based his complaint.

"When a judge denies a motion to dismiss, that's very significant," said Jerrold Parker of Parker Waichman LLP, a national law-firm specializing in mass tort cases. "It means the judge thinks the plaintiffs might have a chance to prevail."

The discovery process, said Parker, will officially determine what 3M and other producers knew about the potential dangers of PFAS and when they knew it.

Lori Swanson, former attorney general in Minnesota, discovered dozens of documents in a pollution lawsuit against 3M that may come into play in the Hardwick case.

Swanson said the documents prove that company's scientists warned of possible toxicity as early as the 1960s, but that 3M did not alert the public to those worries.

The state, while Swanson was in office, filed a $5 billion suit against 3M in 2010 for contamination of several neighborhoods in the east metro area. The state settled the suit with 3M in February 2018 for $890 million.